The present invention relates to a path generation for a motor vehicle.
A path, also called a trajectory, is required for traveling from a starting location to a destination location, along which path a motor vehicle can move. In a conventional manner, current 2D path generators select, from a number of trajectories originating from within predefined boundary conditions, by means of a cost function, that trajectory which meets the cost function in the best manner possible. However, this approach has numerous limitations. Thus, there may be one or more better trajectories which, under the predefined boundary conditions, would be a better trajectory for the path generation, but which are not contained in the number of trajectories. It is further not possible to reliably predict whether the corresponding motor vehicle in general has the physical possibilities of driving along the trajectory determined to be the best possible path. In the case of an autonomously driving motor vehicle, in the following, also called an autonomous vehicle, it is not possible to ensure by the current methods that it is taken into account for the motor vehicle movement whether corresponding actuators to be controlled for the movement of the motor vehicle can be controlled in such a manner that an acceptable direction and/or acceleration change can be carried out.
Problems may further occur in the case of the previously used methods because the resulting final conditions of the actuators are possibly not suitable for continuing the movement in the desired manner. It could happen, for example, that, although the predefined position and orientation of the vehicle are reached on a straight road at the end of the trajectory, the steering may not be in the desired (neutral) position. It would then not be easily possible to stay in the trajectory that follows.
It would therefore be desirable to provide a possibility that eliminates or at least reduces at least one of the above-mentioned limitations.
It is an object of the invention to provide a method which avoids or at least reduces at least some of the disadvantages known in the state of the art.
According to the invention, this object is achieved by a method in accordance with embodiments of the invention.
The object in this case relates to a trajectory planning method for ascertaining a control profile for a motor vehicle, particularly for an autonomously driving motor vehicle. The method has the steps of providing a first position set, the first position set having at least one piece of information with respect to a starting condition at a trajectory start of the trajectory; providing a second position set, wherein the second position set has at least one piece of information with respect to an end condition at a trajectory end of the trajectory; providing a first control set, wherein the first control set has at least one piece of information with respect to a control condition of the motor vehicle at the trajectory start; providing a second control set, wherein the second control set has at least one piece of information with respect to a control condition of the motor vehicle at the trajectory end; providing a vehicle movement modeling function, wherein the vehicle movement modeling function has a kinematic movement model of the motor vehicle; providing a solver ascertaining a control profile information set by applying the solver to the vehicle movement modeling function dependent on the first position set, of the second position set, of the first control set and of the second control set, wherein the control profile information set has two profile information values, and wherein the profile information values are indicative of the trajectory; and determining a control profile for the motor vehicle dependent on the control profile information set, wherein the control profile is indicative of the trajectory.
For the purpose of the invention, a position set may be a set of information which describes the start and the end of a trajectory. As a result, this information may be indicative of the position of a motor vehicle at the start and at the end of the travel along this trajectory.
A trajectory for the purpose of the invention may be a virtual path which is indicative of the route to be covered by a motor vehicle.
In particular, a trajectory can determine which path a motor vehicle is to take. This can particularly be achieved by a plurality of trajectories which can be placed in a mutually adjoining fashion.
For the purpose of the invention, a control set may be a set of information that could be used for controlling actuators of a motor vehicle, in order to move the motor vehicle into a desired direction.
A control condition for the purpose of the invention may be a condition in which an actuator of the motor vehicle is situated. Such a control condition may correspond to a corresponding information of the control set at a defined point in time.
For the purpose of the invention, a vehicle movement modeling function may be a function which can model the movement of a motor vehicle. In a simple case, the vehicle movement modeling function may be an analytical function. In more complex cases, the vehicle movement modeling function may be a non-analytical function. Several functions may also be described for imaging the vehicle movement model, which functions jointly result in the vehicle movement modeling function.
For the purpose of the invention, a kinematic movement model of the motor vehicle may be part of the vehicle movement modeling function. In this case, the kinematic movement model can image the acceleration and braking behavior of a specific motor vehicle or motor vehicle model. Furthermore, additional movement information of the motor vehicle can be imaged in the kinematic model. In a simple case, the kinematic movement model may have one or more analytical functions. In more complex cases, the kinematic movement model may also have one or more non-analytical functions.
For the purpose of the invention, a solver may be a special mathematical program, which can be used for solving a special mathematical problem. For solving a problem, the solver can provide an analytical as well as a numerical approach. Preferably, the solver is a mathematical program which can numerically solve the respective problem.
A control profile according to the invention can carry out the controlling in order to preferably move the motor vehicle along a defined trajectory implicitly contained in the control profile. The control profile may, for example, be a dataset of control-profile-specific information. However, the control profile may also have mathematical functions, from which control information for the motor vehicle control can be determined dependent on the time. The control profile may also have a picture representation of a time-dependent function, from which control information or control values required for the motor vehicle control can be ascertained dependent on the time.
By means of the teaching according to the invention, the advantage is achieved, that a trajectory can be ascertained which can also actually be driven by the motor vehicle.
Before further developments of the invention are discussed in greater detail in the following, it should be noted that the invention is not limited to the described components or the described process steps. Furthermore, the used terminology also represents no limitation but is used only in the manner of an example. To the extent that the singular is used in the specification and in the claims, this also, in each case, comprises the plural, if not explicitly excluded by the context.
The embodiments of the invention may be implemented in various forms of hardware, software, firmware, special purpose processors, or a combination thereof. Aspects of the present invention may be implemented in software as a program tangibly embodied on a program storage device. The program may be a uploaded to, executed by, a machine having any suitable architecture. The machine may be implemented on a computer platform having hardware such as one or more processing units, random access memory, and input/output interfaces. The trajectory planning method that determines the control profile may be executed onboard the motor vehicle, particularly an autonomously driven motor vehicle
Further embodiments of the device according to the invention will be explained in the following.
Corresponding to a first embodiment, the method provides that the first position set has two spatial coordinates and a direction information, the spatial coordinates being indicative of a spatial position of the trajectory at the trajectory start, and wherein the direction information is indicative of a tangent of the trajectory at the trajectory start. The method further provides that the second position set has two spatial coordinates and a direction information, wherein the spatial coordinates are indicative of a spatial position of the trajectory at the trajectory end, and wherein the direction information is indicative of a tangent of the trajectory at the trajectory end.
For the purpose of the invention, a spatial coordinate is an axis designation in a coordinate system. In this case, the coordinate system can usually be selected arbitrarily. For example, a coordinate system with polar coordinates can be selected, as can a coordinate system with non-orthogonal basis vectors. It preferably is a Cartesian coordinate system. In this case, the coordinate system can be used for locally describing a motor vehicle position.
For the purpose of the invention, a direction information is an information concerning an alignment of the motor vehicle in the corresponding location in the space.
In this manner, the beginning of a trajectory can be defined as a motor vehicle position and a motor vehicle alignment at the start of the trajectory. Likewise, the end of the trajectory can be defined as a motor vehicle position and a motor vehicle alignment at the end of the trajectory.
This further development has the advantage that thereby, in a simple and precise manner, the spatial position and spatial alignment of the motor vehicle can be indicated at the desired starting and destination location. Thus, the alignment of the motor vehicle at the corresponding location can be indicated for the route to be traveled, thus the trajectory to be traveled, at the start of the route as well as at the end of the route.
Corresponding to an additional embodiment, the method further provides that the first control set has a first control information which is indicative of a position related to the steering of the motor vehicle at the trajectory start. The method further provides that the second control set has a second control information which is indicative of the position related to the steering of the motor vehicle at the trajectory end.
For the purpose of the invention, the position related to the steering is a control variable which is required for the steering of the motor vehicle. In the simplest case, this may be the angular position of a steering wheel of the motor vehicle. However, the position related to the steering may also be a control variable, for example, an angle of an actuator, to which one or more wheels of the motor vehicle are set or are to be set individually or in pairs.
This embodiment has the advantage that a direct relationship can be established between the trajectory to be driven by the motor vehicle and the motor vehicle steering.
Corresponding to a further embodiment, the method also comprises the steps of dividing the trajectory into a first region and into a second region. In this case, the first region is indicative of an approach phase of the motor vehicle to the trajectory end. In this case, the second region is indicative of a correction phase of the motor vehicle before reaching the trajectory end.
For the purpose of the invention, an approach phase is a first phase of a drive along a route. The approach phase can be modeled according to a natural human driving behavior, particularly a steering behavior and/or acceleration behavior which a driver of the motor vehicle would exhibit for reaching a destination location.
A correction phase according to the invention is a further phase of the drive along the route. In this case, the correction phase can be modeled according to a natural human driving behavior, particularly a steering behavior and/or acceleration behavior, which a driver of the motor vehicle would exhibit in the proximity of the destination location to be reached.
This embodiment has the advantage that the trajectory to be driven can indirectly correspond to a simulation of a motor vehicle driver's natural driving behavior.
Corresponding to a further embodiment, the method also provides that the first profile information value is situated in the approach phase, and that the second profile information value is situated in the correction phase.
This embodiment has the advantage that a control profile can thereby be ascertained which can be modeled according to a motor vehicle driver's natural driving behavior.
Corresponding to a further embodiment, the method also provides that the first profile information value of the control profile information set is indicative of a first point with a horizontal tangent of the control profile, and that the second profile information value of the control profile information set is indicative of a second point with a horizontal tangent of the control profile.
For the purpose of the invention, a point with a horizontal tangent is a point or a location of a mathematical function or curve, which has a slope of zero.
This embodiment has the advantage that it can provide a possibility by which the first region can be differentiated from the second region.
This permits a better simulating of a motor vehicle driver's corresponding natural driving behavior.
Corresponding to a further embodiment, the method provides that the control profile information set has a third profile information value. The third profile information value is indicative of a route of the trajectory.
For the purpose of the invention, a route of the trajectory is the total path of the trajectory. The latter may correspond to the path length to be covered by the motor vehicle in order to drive along the entire trajectory.
This embodiment has the advantage that the motor vehicle can utilize the path length of the trajectory for the determination of the control profile. The control profile can therefore still better model a human driving behavior, preferably an optimal human driving behavior, for the path to be traveled.
Corresponding to a further embodiment, the method further provides that the first control set has a third control information, which is indicative of a speed of the motor vehicle at the trajectory start. Furthermore, the method provides that the second control set has a fourth control information, which is indicative of a speed of the motor vehicle at the trajectory end.
This embodiment has the advantage that several mutually successive trajectories can be determined which, in a simple manner, can be directly connected with one another, because, as a result, the speed at the trajectory end of a first trajectory can be selected to be identical to the speed of a further trajectory to be connected thereto at the trajectory start of the additional trajectory.
Corresponding to a further embodiment, the method provides that the first control set has a fifth control information, which is indicative of a steering rate of the motor vehicle at the trajectory start. The method further provides that the second control set has a sixth control information which is indicative of a steering rate of the motor vehicle at the trajectory end.
A steering rate for the purpose of the invention is a time-dependent change of the steering position, thereby a rate of change of the position of the steering.
This embodiment has the advantage that, for ascertaining the trajectory, it can thereby be specified whether a soft or rather a hard steering behavior is desirable during the drive along the trajectory to be ascertained or of the control profile.
This embodiment further has the advantage that, by specifying the steering rate at the start and at the end of the trajectory, a continuous control rate can be obtained when several trajectories are to be connected to form an overall trajectory.
Corresponding to a further embodiment, the method also provides the determination of a control function of the motor vehicle dependent on the control profile. In this case, the control function is indicative of a desired control of the motor vehicle dependent on the time.
This embodiment has the advantage that a control of the motor vehicle can be permitted from the control profile without any concrete determination of the trajectory.
Corresponding to a further embodiment, the method also provides that the control function has a steering function of the motor vehicle dependent on the control profile. The steering function is indicative of a desired steering of the motor vehicle dependent on the time. The control function further has a speed function of the motor vehicle dependent on the control profile. The speed function is indicative of a desired speed of the motor vehicle dependent on the time.
This embodiment has the advantage that the motor vehicle control can be made possible directly by means of the control profile in order to reach the desired destination position on a defined path, which is modeled according to a motor vehicle driver's driving behavior.
Corresponding to a further embodiment, the method also provides the making available of a secondary-condition set, wherein the secondary-condition set has at least one piece of information concerning a secondary condition of a control of the motor vehicle. The method further provides that the ascertaining of the control profile information moreover takes place dependent on the secondary-condition set.
For the purpose of the invention, a secondary-condition set is a set of information concerning defined values, for example of actuators to be used for the motor vehicle control. These values may, for example, be limit values of these actuators. In this case, this set of information can act as a secondary-condition set for the solver.
This embodiment has the advantage that, by means of it, a control profile can be ascertained that can be navigated even better.
Corresponding to a further embodiment, the method provides that the secondary-condition set is indicative of the limit of a motor vehicle steering, and the secondary-condition set has a first secondary condition, which is indicative of a maximal position of the clockwise steering, and a second secondary condition, which is indicative of a maximal position of the counterclockwise steering.
This embodiment has the advantage that a control profile can thereby be ascertained that can be navigated even better.
The invention thereby permits the determination of a control profile for a motor vehicle in order to reach a desired destination position from a desired starting position. In particular, as a result of a repeated use of the method according to the invention, a control profile can be ascertained for an autonomous motor vehicle, which corresponds to a natural human driving behavior for reaching the destination position. Furthermore, a control profile for the motor vehicle can thereby be ascertained which is unambiguous and navigable.
Established methods do not permit the specification of marginal conditions for the actuators, i.e. to also define the corresponding actuator conditions at the end of the trajectory. Up to now, problems could therefore occur because the resulting end conditions of the actuators may possibly not be suitable for continuing the movement in the desired manner. It could happen, for example, that, although the predefined position and orientation of the vehicle are reached on a straight road at the end of the trajectory, the steering is not in the desired (neutral) position. It would then not be possible to keep on the trajectory that follows. The present invention can eliminate this disadvantage.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.